1. Field of the Invention
The invention relates a terminal to be connected onto a circuit board (hereinafter referred to as connecting terminal) and a method of mounting the same onto the circuit board, particularly to a connecting terminal which is effective in cases where the circuit board is grounded to another circuit board, sealing plate, a chassis, a case frame, and the like so as to prevent an electromagnetic field produced from a high frequency circuit used in a portable telephone and the like from influencing upon other devices, and a method of mounting the connecting terminal onto the circuit board.
2. Description of the Related Art
A grounding terminal has been already known since it has been disclosed, e.g., in Japanese Patent No. 3,068,557 and Japanese Utility Model Registration No. 3,064,756, wherein a grounding terminal is mounted onto a circuit board, i.e., printed circuit board and it comes into compression contact with a grounding conductor, thereby grounding the printed circuit board. FIGS. 6 and 7 show a grounding terminal as disclosed in Japanese Patent No. 3,068,557, wherein FIG. 6 is a plan view showing a state where the grounding terminal is mounted onto a printed-circuit board, and FIG. 7 is a side sectional view taken along the line Axe2x80x2-Axe2x80x2 in FIG. 6. In FIG. 7, designated by 100 is a grounding terminal, 140 a contact part, 141 a restriction part, 160 a wall-like part, 161 a pawl part, 300 a printed-circuit board, 250a, 250b conductive patterns, 260 a soft solder, and 400 a grounding conductor. The grounding conductor 400 is omitted in FIG. 6.
As shown in FIG. 7, the grounding terminal 100 is formed by bending a thin strip metal member. A junction part 120 to be joined to the printed-circuit board 300 is provided on the metal member at substantially the center thereof in the longitudinal direction. The metal member is bent at the junction part 120 in the longitudinal direction so that it has a shape of mountain in cross section and a groove is formed in one surface of the junction part 120. Two junction faces 120a, 120b are formed on both sides of the mountain. The groove is formed in the junction part 120 at the portion remote from the central position thereof in the longitudinal direction by a given interval so that one junction face 120a is smaller than the other junction face 120b. 
The metal member is bent at both ends of the junction part 120 in a direction opposite to the junction faces 120a, 120b. One end of the metal member which is bent at both ends of the junction part 120 is folded back at the end of the junction part 120 to form the contact part 140 and the restriction part 141. The contact part 140 comes into compression contact with the grounding conductor 400 and elastically deformed about a folded back part, namely, turnup part 130 by a given amount in a state where the grounding terminal is soldered to the printed-circuit board 300. FIG. 7 shows a state where the contact part 140 comes into compression contact with the grounding conductor 400 and is elastically deformed. A state where the contact part 140 does not come into contact with a grounding conductor 400 is illustrated by two-dotted one chain line. The contact part 140 comes into compression contact with the grounding conductor 400 by a repulsive force caused by the elastic deformation thereof and becomes conductive to the grounding conductor 400 so that the printed-circuit board 300 is grounded to the grounding conductor 400.
With the construction of the grounding terminal 100, the restriction part 141 is formed on the grounding terminal 100 while continuously connecting to the contact part 140 of the grounding terminal 100 so that the contact part 140 does not exceed an elastic limit when the contact part 140 is elastically deformed. The restriction part 141 comes into contact with the opposite side of the junction face of the junction part 120 at its tip end when the contact part 140 is elastically deformed by a given amount so that the amount of elastic deformation of the contact part 140 is restricted.
With the grounding terminal having such a construction, since the tip end of the restriction part 141 comes into contact with the opposite side of the junction part 120 every time the contact part 140 comes into compression contact with the grounding conductor 400, there arises a possibility that the opposite side of the junction part 120 with which the restriction part 141 comes into contact is injured to induce inferior connection at the junction part 120. Further, since the tip end of the restriction part 141 comes into contact with the opposite side of the junction face when the contact part 140 comes into compression contact with the grounding conductor 400, the moving range of the contact part 140 is restricted, thereby making it difficult to obtain a repulsive force owing to the elastic deformation of the contact part 140, namely, to obtain a given contact pressure between the grounding conductor 400 and the contact part 140.
There occurs a so-called wicking phenomenon where solder is sucked up to the portion close to the turnup part 130 about which the contact part 140 is elastically deformed so that solder is stuck to the portion close to the turnup part 130, thereby impeding the elastic deformation of the contact part 140 to induce the deterioration of spring performance. To cope with such a deterioration of spring performance, the turnup part 130 about which the contact part 140 is elastically deformed is formed at a position remote from the junction part 120 having a small junction area by a given interval. As a result, a solder 260a supplied to the junction face 120a having a small junction area is not sucked up to the turnup part 130 of the contact part 140, thereby preventing the solder 260a from sticking to the turnup part 130. Since the turnup part 130 is formed at the position remote from the small junction face 120a having a small junction area by a given interval, the contact part 140 is to be formed in a specific shape, causing a problem in the formation of the contact part 140. Further, since the solder 260a is stuck to the portion close to the turnup part 130, a peeling force is applied to the solder fixed part every time the contact part 140 is elastically deformed. If the contact part 140 is repeatedly elastically deformed, the solder fixed part is peeled off and cracked, thereby making it difficult to maintain the conduction.
FIG. 8 shows a grounding terminal disclosed in Japanese Utility Model Registration No. 3,064,756. The grounding terminal comprises a substrate part which is mounted on a grounding pattern of a printed-circuit board 350, a spring contact 311 which is protruded integrally from one side of the substrate part to a side confronting the substrate part, and an engaging wall 360 integrally standing upright on the substrate part and engaging with the tip end of the spring contact 311. Since the grounding terminal has the engaging wall 360 engaging with the tip end of the spring contact 311, the engaging wall 360 functions as a stopper relative to an irregular external force which is produced when fingers and the like strike against the spring contact 311, thereby restraining the deformation of the grounding terminal. As a result, it is possible to eliminate such drawbacks that inferior contact is made between the deformed spring contact 311 and a chassis and the like and a storing operation is obstructed which occurred when the spring contact 311 is caught by the chassis when the substrate is stored in the chassis.
However, in cases where the grounding terminal comes into compression contact with a sealed panel and the like from the above when the grounding terminal contacts the sealed panel and the like, the spring contact 311 is not irregularly deformed. However, when the sealed panel and the like is pressed down or compressed oblique or in the lateral direction, which is caused by the deviation of the sealed panel, the spring contact 311 is crushed in the lateral direction and is irregularly deformed, so that there arises a possibility that an elastic force as designed cannot be maintained. Further, the grounding terminal is designed such that the portion where the spring contact 311 actually contacts the sealed panel and the like has an allowable width in a movable (swingable) range of the spring contact 311 at a position higher than the tip end of the engaging wall even if the grounding terminal is rendered in a state where it contacts the sealed panel and the like in the same manner as rendered in a state where it does not contact the sealed panel and the like. However, when the spring contact 311 having such a construction is excessively pressed down by a sealed panel and the like, the tip end of the contact comes into contact with the substrate part, and hence the movable range is limited, making it difficult to keep an optimum elastic force.
Accordingly, it is an object of the invention to solve the problems of the conventional grounding terminal and provide a connecting terminal for allowing a circuit board to come into compression contact with a flat conductor with certainty, particularly to a connecting terminal in which a contact part will not irregularly deformed even if it is pressed down oblique or in the lateral direction, thereby maintaining an optimum contact pressure.
It is another object of the invention to provide a method of mounting the connecting terminal onto a circuit board capable of preventing solder from sticking to a portion close to a curved part owing to a wicking phenomenon where solder is sucked up to the portion close to the curved part about which the contact part is elastically deformed when the connecting terminal is mounted onto the circuit board by soldering, so that the contact part maintains a contact pressure as designed.
To achieve the above objects, the connecting terminal according to a first aspect of the invention is made of a substantially strip conductive plate and comprises a fixed part provided at one end of the conductive plate to be mounted onto a circuit board, and a contact part extended from the fixed part and formed by bending the conductive plate toward the fixed part to form a curved part, said contact part being elastically deformed about the curved part to come into compression contact with a substantially flat conductor, wherein the connecting terminal is characterized in further comprising a pair of side wall parts formed by bending the conductive plate at the fixed part in a width direction thereof, said side wall parts having a height to an extent to restrict excessive deformation of the contact part when the contact part comes into compression contact with the flat conductor. With such a construction, if the connecting terminal comes into compression contact with the flat conductor, an excellent contact is maintained between the contact part and the flat conductor. Further, even if an excessive compression force is applied to the contact part, the flat conductor is restricted by the side wall parts, thereby preventing permanent deformation of the contact part.
The connecting terminal of the invention is characterized in that an interval between the side wall parts is made larger than a width of the contact part, and both end sides of the contact part contact or approach inner side walls of the side wall parts when the contact part comes into compression contact with the flat conductor. With such a construction, the connecting terminal can allow the circuit board to come into compression contact with the flat conductor with certainty. Particularly, even if the contact part comes into compression contact with the flat conductor oblique or in the lateral direction, the contact part will not irregularly deformed so that an optimum contact pressure can be maintained.
The connecting terminal of the invention is characterized in further comprising projection pieces provided on the conductive plate in the width direction close to the curved part between the fixed part and the curved part. If the connecting terminal is mounted onto the circuit board, the projection pieces come into contact with the circuit board, thereby realizing stable mounting.
A connecting terminal according to a second aspect of the invention is made of a substantially strip conductive plate and comprises a fixed part provided at one end of the conductive plate to be mounted onto a circuit board, and a contact part extended from the fixed part and formed by bending the conductive plate toward the fixed part to form a curved part, said contact part being elastically deformed about the curved part to come into compression contact with a substantially flat conductor, wherein the connecting terminal is characterized in further comprising a notch defined and separating between the fixed part and the curved part, said fixed part and the separated part being connected to each other by a pair of side wall parts formed by bending the conductive plate in the width direction thereof toward the contact part.
The connecting terminal of the invention is characterized in that a plurality of notches are defined in the fixed part for cutting off the fixed part into a plurality of fixed parts and separated part, said fixed parts and the separated part being connected to each other by a pair of side wall parts formed by bending the fixed part in the width direction thereof toward the contact part.
Further, the connecting terminal of the invention is characterized in that the side wall parts have a height to an extent to restrict excessive deformation of the contact part when the contact part comes into compression contact with the flat conductor. With such a construction, if the connecting terminal comes into compression contact with the flat conductor, an excellent contact is maintained between the contact part and the flat conductor, and further, even if an excessive compression force is applied to the contact part, the flat conductor is restricted by the side wall parts, thereby preventing permanent deformation of the contact part.
The connecting terminal of the invention is characterized in that the interval between the side wall parts is larger than a width of the contact part, and both end sides of the contact part contact or approach inner surfaces of the side wall parts when the contact part comes into compression contact with the flat conductor. With such a construction, even if the contact part comes into compression contact with the flat conductor oblique or in the lateral direction, the contact part will not irregularly deformed, thereby maintaining an optimum contact pressure.
Further, the connecting terminal of the invention is characterized in further comprising projection pieces provided on the conductive plate in the width direction close to the curved part between the fixed part and the curved part.
Still further, the method of mounting a connecting terminal onto a conductor of a circuit board according to the invention is characterized in comprising preparing a connecting terminal used in the second aspect of the invention and fixing bottom surfaces of a plurality of separated fixed parts to the conductor of the circuit board by soldering except the separated part close to a curved part of the plurality of separated fixed parts. With such a construction, the connecting terminal is fixed between the fixed parts and the conductive pattern by soldering but it is not fixed at the separated part close to the curved part by soldering. Accordingly, there does not occur a case where solder at the fixed part is sucked up to a curved part owing to a wicking phenomenon when the connecting terminal is mounted onto the circuit board so that spring performance is not changed, and contact pressure of the contact part relative to the counterpart, i.e., flat conductor can be maintained at numerical values substantially the same as designed. Further, since the solder is not stuck to the curved part, it is possible to completely avoid a drawback of the occurrence of the crack owing to the sticking of the solder onto the curved part which has been made in the prior art.